Embodiments of the present invention relate to processing units, for example micro-controllers.
Security controllers are threatened by a plurality of attacking scenarios. One possible kind of attack is the permanent modification of a circuit, for example via a focused ion beam (FIB). Using FIBs, it is possible to, for example, permanently connect signal paths of the security controller or any other micro-controller or processing unit to a high or low voltage, with other signal paths or to disconnect signal paths to modify the functional behavior of the processing unit. This kind of permanent modification or manipulation of the functionality of processing units can, for instance, be used for fraud in the context of payment cards, security or authentication cards, or any other misuse where third parties rely on the proper functioning of the processing unit or device, e.g. in a gas counter at a gas station, in a weighing machine, etc.
One known method for detecting such permanent manipulations is the “user mode security life control” (UmSLC). Here, the system is stopped in regular or irregular intervals and parts of the circuitry are checked using patterns specifically added to the circuitry that are conducted through the system and that are readout and checked. Such solutions require additional hardware, for example for the storage of the results. Furthermore, a considerable amount of downtime for the testing of the nodes is required, and sometimes it is even impossible to integrate such solutions.
Equal or equivalent elements are denoted in the following description of the figures by equal or equivalent reference signs.